We investigate possible manifolds characterizing traversable wormholes in the presence of a scalar field, which is minimally coupled to gravity and has both kinetic and potential energy. The feature ...of traversability requires the violation of the null energy condition, which, in turn, signals the existence of exotic matter with negative energy density. For this reason, we impose a hypothetical Casimir apparatus with plates positioned at a distance either parametrically fixed or radially varying. The main feature of all the derived solutions is the conservation of the Stress Energy Tensor. Such a conservation though requires the introduction of an auxiliary field, which we interpret as a gravitational response of the Traversable Wormhole to the original source. Interestingly, the only case that seems to avoid the necessity for such an auxiliary field, is the one involving a scalar field with a potential, in combination with a Casimir device with fixed plates.
Purpose The aim of this study is to present developed tools that are necessary to determine and verify dose‐response parameters of tumors and healthy tissues. Furthermore, this software uses this ...radiobiological information in order to compare and optimize several treatment plans. Material and Methods One part of the software determines the dose‐response parameters for tumors and healthy tissues. The dose distributions of each patient are associated with their follow‐up results in a maximum likelihood fitting, which calculates the best estimates and confidence intervals of the model parameters. Another part is used to validate reported dose‐response parameters. The software uses local dosimetric and treatment outcome data and associates them with published radiobiological parameters using various statistical methods (χ2‐test, ROC, odds ratio etc). The third part is used to estimate and increase the likelihood of complication‐free tumor control, P
+ by plotting the response curves of the control, complication and P
+ probabilities using the mean dose to the target on the dose axis. Results Head & neck and prostate cancer cases are used to show the clinical usefulness of this radiobiological tool in treatment plan comparison. The compatibility of the examined treatment methodologies with a set of reported dose‐response parameters was confirmed using the appropriate module of the software. The prescribed dose levels were determined by renormalizing the treatment plans until the P
+ index became maximal. A more conformal dose delivery to the target shows that a higher control rate is achieved for the same complication level. Conclusions The described tool is proved to be useful and effective in the clinical application of radiobiological modeling. Furthermore, it can be applied in the development of clinical information databases and for performing epidemiological studies assisting the cooperation between different institutions in order to produce research and clinical frameworks.
In order to apply highly conformal dose distributions, which are characterized by steep dose fall-offs, it is necessary to know the exact target location and extension. This study aims at evaluating ...the impact of using combined CT-MRI images in organ delineation compared to using CT images alone, on the clinical results. For 10 prostate cancer patients, the respective CT and MRI images at treatment position were acquired. The CTV was delineated using the CT and MRI images, separately, whereas bladder and rectum were delineated using the CT images alone. Based on the CT and MRI images, two CTVs were produced for each patient. The mutual information algorithm was used in the fusion of the two image sets. In this way, the structures drawn on the MRI images were transferred to the CT images in order to produce the treatment plans. For each set of structures of each patient, IMRT and 3D-CRT treatment plans were produced. The individual treatment plans were compared using the biologically effective uniform dose () and the complication-free tumor control probability (P+) concepts together with the DVHs of the targets and organs at risk and common dosimetric criteria. For the IMRT treatment, at the optimum dose level of the average CT and CT-MRI delineated CTV dose distributions, the P+ values are 74.7% in both cases for a of 91.5 Gy and 92.1 Gy, respectively. The respective average total control probabilities, PB are 90.0% and 90.2%, whereas the corresponding average total complication probabilities, PI are 15.3% and 15.4%. Similarly, for the 3D-CRT treatment, the average P+ values are 42.5% and 46.7%, respectively for a of 86.4 Gy and 86.7 Gy, respectively. The respective average PB values are 80.0% and 80.6%, whereas the corresponding average PI values are 37.4% and 33.8%, respectively. For both radiation modalities, the improvement mainly stems from the better sparing of rectum. According to these results, the expected clinical effectiveness of IMRT can be increased by a maximum ΔP+ of around 0.9%, whereas of 3D-CRT by about 4.2% when combined CT-MRI delineation is performed instead of using CT images alone. It is apparent that in both IMRT and 3D-CRT radiation modalities, the better knowledge of the CTV extension improved the produced dose distribution. It is shown that the CTV is irradiated more effectively, while the complication probabilities of bladder and rectum, which is the principal organs at risk, are lower in the CT-MRI based treatment plans.
Abstract
Background
Peri-device leaks (PDL) are quite common after left-atrial appendage occlusion (LAAO) given the complex anatomy of LAA and surrounding structures. However, there is uncertainty ...regarding the prognostic implications of PDL.
Material and methods
Literature search was conducted in MEDLINE (PubMed), EMBASE, Scopus by ELSEVIER and Cochrane Central Register of Controlled Trials (CENTRAL) databases until 12 October 2021. A random-effects meta-analysis was performed to assess the effect of PDL presence on thromboembolism, all-cause mortality and major bleeding occurrence. Sensitivity analyses accounted for: i. the combined AF ablation performance, ii. the anticoagulation strategy followed after LAAO, iii. mean PDL size, and iv. mean female percentage.
Results
Of 699 articles initially retrieved, 46 were deemed eligible for this analysis (9,184 AF patients undergoing LAAO out of whom 1,446 had PDL). PDL presence was significantly associated with elevated odds of thromboembolism (FIgure 1) pooled odds ratio (pOR) 3.05, 95% confidence interval (CI) 1.94–4.81; I2=37%; yet PDL was not significantly linked with mortality (pOR=0.86, 95% CI: 0.25–2.95; I2=69%) and major bleeding rates (0.95, 95% CI: 0.27–3.35; I2=72%). AF-ablation did not significantly interact with the prognostic impact of PDL when performed in conjunction with LAAO (p for subgroup= 0.17). Antiplatelet discharge medication affected the prognostic value of PDL (p for subgroup <0.01 and =0.04, respectively). The prognostic significance of mean PDL size peri-procedural or at 1–3 months or D(mean size)/D(time of follow-up) on the risk of thromboembolism did not yield any significant association (p values >0.05). Meta-regression analysis of the mean female percentage demonstrated a non-significant trend towards a positive linear correlation between female percentage and risk of thromboembolism (p=0.10) (FIgure 2).
Conclusions
This is the first meta-analysis on the prognostic impact of PDL after LAAO. The findings highlighted a significant association between PDL and thromboembolic events, warranting careful post-LAAO device surveillance.
Funding Acknowledgement
Type of funding sources: None.
Abstract
Background
Atrial fibrillation (AF) and valvular heart disease (VHD) are frequently encountered in clinical practice, and often coexist, especially in the elderly population. Both conditions ...are associated with increased mortality and morbidity. Recent guidelines suggest careful evaluation of patients with AF and VHD due to the puzzling nature of their coexistence.
Purpose
To evaluate the prognostic effect of significant valvular heart disease (sVHD) among patients with non-valvular AF.
Methods
This is a post-hoc analysis of the MISOAC-AF trial (NCT02941978). Consecutive inpatients with non-valvular AF who underwent echocardiography were included. sVHD was defined as the presence of at least moderate aortic stenosis (AS) or aortic/mitral/tricuspid regurgitation (AR/MR/TR). Cox regression analyses with covariate adjustments were used for outcome prediction.
Results
In total, 983 patients with non-valvular AF (median age 76 years) were analyzed over a median follow-up period of 32 months. sVHD was diagnosed in 575 (58.5%) AF patients. sVHD was associated with all-cause mortality (21.6%/yr vs. 1.6%/yr; adjusted HR aHR 1.55, 95% confidence interval CI 1.17–2.06; p=0.02), cardiovascular mortality (16%/yr vs. 4%/yr; aHR1.70, 95% CI 1.09–2.66; p=0.02) and heart failure-hospitalization (5.8%/yr vs. 1.8%/yr; aHR 2.53, 95% CI 1.35–4.63; p=0.02). The prognostic effect of sVHD was particularly evident in patients aged <80 years and in those without history of heart failure (p for interaction <0.05, in both subgroups) Figure 1. After multivariable adjustment, moderate/severe AS and TR were associated with mortality, while AS and MR with heart failure-hospitalization Figure 2. AS was the only independent predictor of valve intervention during follow-up (aHR 10.78, 95% CI 4.80–24.22; p<0.001). Mixed aortic valve disease (AS+AR) had superior prognostic power across patterns of combined VHD.
Conclusions
Among patients with non-valvular AF, sVHD was highly prevalent, and beared high prognostic value across a wide spectrum of clinical outcomes. AS, MR, TR and mixed aortic valve disease were associated with worse prognosis.
Funding Acknowledgement
Type of funding sources: None. Subgroup analyses by VHD statusPrognostic impact of valve lesions
Aims
New-onset left bundle branch block (LBBB) and complete atrioventricular block (AV3B) frequently occur following transcatheter aortic valve implantation (TAVI). We sought to determine the timing ...and potential mechanisms of new conduction abnormalities (CAs) during TAVI, using the Medtronic CoreValve System (MCS).
Methods and results
Sixty-five consecutive patients underwent TAVI with continuous 12-lead ECG analysis. New CAs were defined by the occurrence of LBBB, RBBB, and/or AV3B after the following pre-defined time points: (i) crossing of valve with stiff wire, (ii) positioning of balloon catheter in the aortic annulus, (iii) balloon valvuloplasty, (iv) positioning of MCS in the left ventricular outflow tract (LVOT), (v) expansion of MCS, (vi) removal of all catheters. A new CA occurred during TAVI in 48 patients (74%) and after TAVI in 5 (8%). Of the 48 patients with procedural CAs, a single new CA occurred in 43 patients (90%) and two types of CAs in 5 (10%). A new LBBB was seen in 40 patients (83%), AV3B in 9 (19%), and RBBB in 4 (8%). The new CA first occurred-in descending order of frequency-after balloon valvuloplasty in 22 patients (46%), MCS expansion in 14 (29%), MCS positioning in 6 (12%), positioning of balloon catheter in 3 (6%), wire-crossing of aortic valve in 2 (4%), and after catheter removal in 1 patient (2%). Patients who developed a new CA during balloon valvuloplasty had a significantly higher balloon/annulus ratio than those who did not (1.10 ± 0.10 vs. 1.03 ± 0.11, P = 0.030). No such relationship was found with the valve/annulus ratio.
Conclusion
Transcatheter aortic valve implantation with the MCS was associated with new CAs in 82% of which more than half occurred before the actual valve implantation. It remains to be elucidated by dedicated studies whether new CAs can be reduced by appropriate balloon sizing-a precept that also holds for valve size given the observed directional signal of the valve size/aortic annulus ratio.
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